The present invention relates to a valve operating device for an engine of a vehicle, particularly a valve operating device which switches a cam for opening and closing a valve.
A type of valve operating device for an engine is known, which is provided with a plurality of cams having nose parts in different shapes for each valve, and for switching opening degrees and open and close timings of intake and exhaust valves by selecting the cam for opening and closing the valves among the plurality of cams, according to an operating state of the engine.
For example, US2011/0226205A1 discloses such a valve operating device. The valve operating device includes a camshaft comprised of a shaft and a cylindrical cam element spline-fitted onto the shaft and slidable in axial directions along the shaft. For each valve, a plurality of cams, each having a nose part in a different shape, are provided adjacent to each other in the outer circumference of the cam element. The valve operating device switches the cam for opening and closing the valve by sliding the cam element in one of the axial directions.
In this case, in the valve operating device of US2011/0226205A1, an end face cam is formed in both end faces of the cam element, and control members, each comprised of a pin member, are provided to be able to enter into and retreat from respective positions adjacent in the axial directions to the end face cams and push the cam element to respective sides in the axial directions by engaging with the end face cams in the entry. The valve operating device switches the cam by operating the control member with an actuator.
Meanwhile, recently, with engines each including such a valve operating device described above, it has been desired to switch to an optimal cam per unit of combustion cycle according to an operating state of the engine, in other words, successively and instantaneously switch the cam. In this case, in the valve operating device of US2011/0226205A1, it is required to operate, with good responsiveness, control devices provided on both sides of the cam element, each comprised of the control member and an actuator. Specifically, after the cam element is slid to one side in one of the axial directions by one of the control devices, when sliding the cam element in the other direction by the other control device, in order to avoid interference between the control member of the control device that slid the cam element first and the cam element, it is required to swiftly retreat the control member that slid the cam element first.
However, with the actuator of the control device, for which a solenoid is used, a response delay is caused between an output of a retreat signal and the retreat of the control member. Therefore, with the valve operating device of US2011/0226205A1, the retreat of the control member cannot be completed swiftly; thus, it has been difficult to satisfy the above-described desire, particularly in a high speed operation of the engine where a period of time for one cycle is short. Moreover, if the actuator is increased in size so as to accelerate the retreating speed of the control device, disadvantages of increased cost and difficulty of engine installation will arise.
Moreover, these disadvantages are not limited to valve operating devices including end face cams on both end faces of a cam element and control devices for pushing the end face cams. Similar disadvantages to the above arise even with valve operating devices formed with an end face cam on only one end face of a cam element and a control device for pushing the end face cam, and a different component for pushing the cam element from the other end face.